Bartosz,
Laurent was mentioning the installTapOnBus. Your published code would not need
that. You are just playing MIDI. You would be concerned if you had to do custom
real-time audio processing on the audio output of your MIDI device (such as FFT
analysis).

Arshia
> On 11 Jul 2018, at 16:04, Bartosz Nowotny <bartosznowo...@gmail.com> wrote:
>
> Laurent,
>
> What you said about not being able to achieve latency lower than 100ms is
> worrisome. I need a realtime MIDI synth, low latency is absolutely crucial.
> Does the limitation you mention apply only to signal processing or other
> applications of the API as well, in particular MIDI synthesis?
>
> Regards,
> Bartosz
>
>
> On Wed, Jul 11, 2018 at 3:30 PM, Laurent Noudohounsi
> <laurent.noudohou...@gmail.com <mailto:laurent.noudohou...@gmail.com>> wrote:
> Thanks Benjamin for the precision. I thought that `installTapOnBus` was the
> successor of `RenderCallback`.
> For me it was not natural to mix old api like
> `kAudioUnitProperty_SetRenderCallback` in AVAudioEngine.
>
> So as Arshia said, I'm also looking for a way to use real-time processing
> with AVAudioEngine.
>
> Le mer. 11 juil. 2018 à 15:05, Arshia Cont <arshiac...@antescofo.com
> <mailto:arshiac...@antescofo.com>> a écrit :
> Interesting thread here!
>
> Anyone has achieved low-latency processing on AVAudioEngine?
>
> The RenderCallback seems natural to me (which is the good “old” way of doing
> it with AUGraph). But I’m curious to hear if anyone has done/achieved real
> stuff here with AVAudioEngine real-time processing and how.
>
>
> Arshia
>
>
>> On 11 Jul 2018, at 15:00, Benjamin Federer <benja...@boinx.com
>> <mailto:benja...@boinx.com>> wrote:
>>
>> Laurent,
>>
>> `installTapOnBus` is not intended for realtime processing as a tap only
>> provides the current frame buffer but does not pass it back into the signal
>> chain. The documentation reads `Installs an audio tap on the bus to record.
>> monitor, and observe the output of the node`.
>>
>> Although I have not done that myself yet my understanding is that for
>> realtime processing you can still retrieve the underlying audio unit from an
>> AVAudioNode (or at least some nodes?) and attach an input render callback
>> via AudioUnitSetProperty with kAudioUnitProperty_SetRenderCallback.
>>
>> I assume the other way would be to subclass AUAudioUnit and wrap that into
>> an AVAudioUnit which is a subclass of AVAudioNode. Yes, it confuses me, too.
>> Random Google result with further information:
>> https://forums.developer.apple.com/thread/72674
>> <https://forums.developer.apple.com/thread/72674>
>>
>> Benjamin
>>
>>
>>> Am 11.07.2018 um 14:34 schrieb Laurent Noudohounsi
>>> <laurent.noudohou...@gmail.com <mailto:laurent.noudohou...@gmail.com>>:
>>>
>>> Hi all,
>>>
>>> I'm interested in this topic since I've not found any information about it
>>> yet.
>>>
>>> Correct me if I'm wrong but AVAudioEngine is not able to lower than 100ms
>>> latency. It's what I see in the header file of `AVAudioNode` with its
>>> method `installTapOnBus`:
>>>
>>> @param bufferSize the requested size of the incoming buffers in sample
>>> frames. Supported range is [100, 400] ms.
>>>
>>> Maybe I'm wrong but I don't see any other way to have a lower latency audio
>>> processing in an AVAudioNode.
>>>
>>> Best,
>>> Laurent
>>>
>>> Le mer. 11 juil. 2018 à 13:57, Arshia Cont <arshiac...@antescofo.com
>>> <mailto:arshiac...@antescofo.com>> a écrit :
>>> Benjamin and list,
>>>
>>> I double Benjamin’s request. It would be great if someone from the
>>> CoreAudio Team could respond to the question.
>>>
>>> Two years ago, after basic tests I realised that AVAudioEngine was not
>>> ready for Low Latency Audio analysis on iOS. So we used AUGraph. I have a
>>> feeling that this is no longer the case on iOS and we can move to
>>> AVAudioEngine for low-latency audio processing. Anyone can share experience
>>> here? We do real-time spectral analysis and resynthesis of sound and go as
>>> low as 64 samples per cycle if the device allows.
>>>
>>> Thanks in advance.
>>>
>>>
>>> Arshia
>>>
>>>
>>> PS: I actually brought the deprecation issue of AUGraph in a local Apple
>>> Dev meeting where the EU director of developer relation was present.
>>> According to him, when Apple announces a deprecation, it WILL happen. My
>>> interpretation of the conversation is that AUGraph is no longer maintained
>>> but provided as is.
>>>
>>>> On 11 Jul 2018, at 12:36, Benjamin Federer <benja...@boinx.com
>>>> <mailto:benja...@boinx.com>> wrote:
>>>>
>>>> Since it was mentioned in another email (thread) I’m giving this topic a
>>>> bump. Would be great if someone at Apple, or anyone else in the know,
>>>> could take the time to respond. The documentation at the link cited below
>>>> still has no indication of deprecation. Will it come with one of the next
>>>> Xcode Beta releases?
>>>>
>>>> On another note I am really interested in how transitioning over to
>>>> AVAudioEngine is working out for everyone. I know AVAudioEngine on iOS.
>>>> What I am interested in is any macOS specifics or hardships.
>>>>
>>>> From my experience AVAudioEngine is relatively robust in handling multiple
>>>> graphs, i.e. separate chains of audio units. I had some issues with the
>>>> AVAudioPlayerNode connecting to multiple destinations in that scenario.
>>>> Also connect:toConnectionPoints:fromBus:format: did not work for me as it
>>>> only connected to one of the destination points. Anyone else experienced
>>>> problems in that regard?
>>>>
>>>> Thanks
>>>>
>>>> Benjamin
>>>>
>>>>
>>>>> Am 08.06.2018 um 16:59 schrieb Benjamin Federer <benja...@boinx.com
>>>>> <mailto:benja...@boinx.com>>:
>>>>>
>>>>> Last year at WWDC it was announced that AUGraph would be deprecated in
>>>>> 2018. I just browsed the documentation
>>>>> (https://developer.apple.com/documentation/audiotoolbox?changes=latest_major
>>>>>
>>>>> <https://developer.apple.com/documentation/audiotoolbox?changes=latest_major>)
>>>>> but found
>>>>> Audio Unit Processing Graph Services not marked for deprecation. The
>>>>> AUGraph header files rolled out with Xcode 10 beta also have no mention
>>>>> of a deprecation in 10.14. I searched for audio-specific sessions at this
>>>>> year’s WWDC but wasn’t able to find anything relevant. Has anyone come
>>>>> across new information regarding this?
>>>>>
>>>>> Judging by how much changes and features Apple seems to be holding back
>>>>> until next year I dare ask: Has AUGraph API deprecation been moved to a
>>>>> later time?
>>>>>
>>>>> Benjamin
>>>>
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